Grinding apparatus for precious stone working



March 17, 1964 E. w. ONEAL 3,125,088

GRINDING APPARATUS FOR PRECIOUS STONE WORKING Filed Aug. 17, 1962 INVENTOR.

- EDWIN W. O'NEAL BY A ATTORNEXS United States Patent Thisinvention relatestoa grinding cup for precious stone working. More specifically, this invention relates to a grinding. cup for grinding, sanding, and otherwise finishing precious and semi-precious gem stones.

Finished gem stones are generally divided .into two basic types according to the stylein which it is cut: The

cabochon stones, or those having rounded or oval configuration, and the facetedstones, or those having a multiplicity of intersecting plainersurfaces or facets. It is the grindingand finishing of these gem stones with which this invention is concerned.

The cutting of a cabochon, for instance, generally requires the following procedure: (1) The rough gem material is sawed into rough slabs or slices; (2) Each slab .or slice is rough ground to its approximate finished shape;

(3) The ground, shaped, rough gem stone is then dopped onto the business end of a dop stick; (4) The dopped, rough ground gem stone is thenfinish ground; (5) The gem stone isthen both rough and finish sanded; (6) .The

stone is then polished; and (7) Finally thegem stone is removed from the dopv stick and thoroughly cleaned.

The cutting of a faceted stone. follows the. same general procedure as that outlined above for the cutting of cabochons with but slight modifications, and generally uses the same type of equipment. 'Generally,.each of the steps in the cutting of both types of stones requires a diiferent apparatus; for example, in the grinding and sanding of gem stones, abrasive wheels and sanding discs of varying degrees of grit are required while also still another wheel or buff, having embedded therein a conventional polishing powder or compound, is required for the finish polishing of the gem stone. These grinding, sanding and polishing apparatuses are commonly connected to and driven by one or more conventional electrical motors. These apparatuses can be mounted on separate motors or can be alternately connected to a single, common motor as the above outlined cutting operation progresses. It should be evident that providing a separate drive motor for each apparatus would prove costly and would also require enlarged working space in the lapidary shop. On the other hand, if a single drive motor is used for operating the various grinding, sanding and polishing apparatuses, much time would be expended in dismounting one apparatus from the motor and replacing it with the next apparatus to be used in the cutting operation.

Therefore, it is one object of this invention to provide an apparatus for working gem stones that allows combining two or more of the conventional gem stone cutting steps outlined above, thereby reducing cutting time and expense.

Yet another object of this invention is to provide an apparatus for working gem stones that enables the lapidist to progress through the grinding, sanding and the polishing steps of the cutting operation without having to shut off the motor driving the apparatus.

Still another object of this invention is to provide a grinding cup for working or cutting gem stones that can be used for fine grinding, sanding and polishing of the stones by simply changing the grinding element of the cup.

A'further object of this invention is to provide a grinding cup for grinding or cutting cabochon and faceted gem stones, the grinding element of which can be changed according to the requirements of the cutting operation without stopping the grinding cup drive motor.

A still further object of this invention is to provide a grinding cup for cutting cabochon gem stones, such cup :being composed of an outer metallic cup and an inner wooden cup having ,a working surface in whichappropriate abrasive material is embedded. The inner cup isremovablefrom, the outer cup to allow replacing itwith a -wooden cup having a diiferentsizeabrasive grit and hence .proceed from one step to the next in the cutting operation without the necessity of stopping the drive motor.

Another object of this invention, is to provide a grind- .ing lap for cutting faceted gam stones composed of an outer metalliccup and an inner cylindrical cutting element removably received within the metallic cup. The upper flat surface of the cutting element serving asthe gem stone cutting surface.

Further objects and advantages of this invention will be apparent from the following description and appended claims, reference being had to the accompanying drawing forming a part of this specification.

FIGURE lis a partial cross-sectional exploded .view

of the grinding cup of this invention.

FIGURE 2 is .an elevational, partial cross-sectional view of an alternative grinding or lap elementfor use in accordance with this invention.

.Referring now to FIGURE 1, thereis shown one. em-

bodiment of the grinding cup of this invention which consists of the combination of metallic cup member A and wooden cup member B. Metallic cup member A consists of cylindrical wall portion .lltl closed by cylindrical bottom portion 12. Depending from bottom portion 12 wheel 19. Clearly, it is preferred that bore 16 be threaded such that rotation of the polishing wheel will tend .to

tighten the connection of metallic cup member A upon the exposed threads of the polishing wheel shank. It must be understood that any other convenient attaching means may be used for connecting cup member A to the polishing wheel such as, for example, a pin or set screw extending through shank l4 and the polishing wheel drive shaft (not shown).

An externally upset annular portion 18 is provided at the bottom of cylindrical side portion 10 of metallic cup member A. This upset portion 13 is provided with knurls or similar serrations which facilitate the operator in hand tightening cup member A upon the exposed threads of the grinding and polishing wheel.

Wooden cup member B is preferably prepared from a hard wood such as maple. Cup member B is essentially a cylindrical block of wood 20 having a bore 22 extending into the upper portion of the block 20 coaxially therewith. Located at the upper extremity of the wooden block 20 is an outwardly extending annular flange or lip portion 24 the purpose of which will be more fully described hereinafter. The external diameter of block 20 is slightly less than the internal diameter of cup member A so that cup member B can be easily inserted into and removed from cup member A.

In preparing cup member B, conventional wood working procedures are followed. For instance, cup member B can be turned on a conventional wood lathe. It has been found that a more accurate centering of bore 22 in block 20 is obtained by turning, drilling or otherwise forming bore 22 before shaping the outside of block 20.

It is preferred that cup member B be prepared such that its central axis is parallel to the grain of the wood. It has been found that cups so prepared have little tendency to swell due to increased temperature or moisture absorption, or if they do swell, they swell evenly. Therefore, they tend to align themselves better within cup member A than those cup members whose central axis lies at an angle to the grain of the wood. Also, those cup members whose axis is parallel to the grain of the wood exhibit considerably more strength than those whose axis lies at an angle to'the grain of the wood.

Although cup member B fits rather loosely within cup member A, it has been found that there is relatively no slippage between the two cup members A and B respectively as they rotate. It appears that the pressure of the dopped stone against the working surface of cup member B results in a strong frictional drag between the cup member B and cup member A, thereby preventing slippage between them during the cutting operation. The cup member B is preferably designed such that the distance from the bottom of the cup to the underside of the lip portion 24- is slightly greater than the inside depth of the receiving cup member A. Hence, the frictional forces will operate against the sides and bottom of the cups.

Working bore 22 of cup member B has a relatively smooth, cylindrical side wall surface 26 and a smooth, concave bottom surface 28. In use, conventional cabochon grinding, sanding or polishing abrasives become embedded in surfaces 26 and 2.8 to provide the working surfaces for the cabochon.

t should be noted that a plurality of cup members B having embedded in the working surfaces 26 and 28 thereof abrasives of varying types and grit sizes will be required when the grinding cup of this invention is used in performing the fine grinding and finishing.

Although bore 22 has been described as having a side wall surface 26 that is substantially cylindrical and a bot tom surface 28 that is substantially concave, surfaces 26 and 2b can assume a multiplicity of varying shapes without departing from the spirit and scope of this invention. For instance, surface 26 can be provided with one or more annular grooves and/or ridges (not shown) and surface 28 can be flat or convex without materially altering the use and operation of this invention.

Furthermore, it should be obvious to one skilled in the art that the internal diameter of bore 22 will depend upon the size of the cabochon to be cut therein; the larger stones requiring a bore with a larger diameter. Therefore, it may prove desirable, though not always necessary, to have a plurality of cup members B having central bores 22 of varying diameters and configurations.

Referring now to FIGURE 2, there is shown another embodiment of this invention consisting of an accurately machined metal lap C for the cutting of facet gem stones. Facet cutting and polishing laps are commonly made from cast iron, brass, copper, or combinations of these metals. These laps are charged on their flat cutting surface with a paste of an appropriate cutting or polish ing grit or abrasive material and a liquid such as olive oil or water.

The improved lap C of this invention consists of a relatively short metallic cylinder 30 having an upper annular flange portion 32. Upper flat surface 34 of lap C is charged in a conventional manner with an abrasive paste 36 of the type just described. Therefore, treated surface 34 serves as the grinding or polishing surface for working facet gem stones, depending upon the type of paste 36 that has been applied to surface 34.

Cylinder 30 is removably receivable the upper cylindrical portion It of metallic cup member A with flange portion 32 serving as a stop member for abutting engagement with the upper edge 1:1 of cylindrical portion 10. It should be appreciated that cylinder 39' can be machined to substantially fill cylindrical portion of cup member A, but in the interest of economy of manufacture it is desirable to make it only sufficiently long axially that it will be retained within and rotate with cup member A by friction of the upper end of cup member A and the underside of portion 32. Lap C will rotate with cup member A relatively free from slippage but can be easily removed by grasping the peripheral edge 33 of flange portion 3 2 and applying an upward force thereto. Clearly then, lap C can be removed and replaced by a different lap having different grinding or polishing properties accordingly as the cutting operation progresses or new and different stones are to be worked while the cup member A continues to rotate.

Operation In the operation of this invention, cup member A is screw threaded upon the exposed threads 17 on the end of the shaft of a conventional tank-type horizontally rotating grinding and polishing wheel 19. Wooden member B is then placed within cup member A when a cabochon is to be worked or lap C is placed therein when a facet stone is to be worked. The grinding and polishing wheel drive motor is then started, subjecting the combination of cup member A and member B or lap C to rotation about their common axis. Grinding dust and abrasives, appropriate for the purpose to which the grinding cup is to be used, is then placed within the bore 22 of wooden cup member B. These abrasives become embedded in use within the wood surfaces 26 and 28 and are thereafter useful for grinding, sanding or polishing of the gem stone. Small amounts of abrasives may be periodically added to :bore 22. as required by the lapidist during the cutting or polishing of the stones. It must be understood that grinding or polishing surface 34 of lap C is conventionally charged with the abrasive paste 36 prior to placing the lap C within cup member A.

The type of abrasive to be used will depend upon the operation to be performed by the grinding cup. For example, silicon carbide dust :and diamond dust of varying grit size are commonly used for grinding and sanding gem stones, whereas, powdered tripoli and tin oxide are the preferred polishing agents.

Whenever one step in the cutting or grinding operation is completed and it is desired to proceed or repeat the next following step in which an abrasive of different grit size or different type is required, all that is required is that the operator remove wooden cup member B, or lap C, depending upon the type of stone being worked, and replace it with a similar cup member, or lap, which has been previously treated with the appropriate abrasive material.

In removing one cup or lap after its usefulness in the gem stone cutting operation has been realized it is no longer required to stop the entire apparatus. All that is required with the grinding cup of this invention is that the cup member B or lap C simply be lifted from metallic cup member A while metallic cup member A is rotating. The wooden cup member or lap to be next used is then easily inserted into metallic cup member A as cup member A continues to rotate. The newly inserted wooden cup member or lap will immediately commence to rotate with metallic cup member A and will automatically seat itself therein, whereupon it will be ready for the next succeeding step in the gem stone cutting operation.

Annular flange portion 24 on the upper end of wooden block 20 is used primarily to assist in removing cup member B from cup member A in a manner similar to that described above for the removal of lap C from cup member A. In so doing flange portion Z4 may be grasped by the operator and an upward pull exerted thereon to remove cup member B from cup member A. Alternatively a thin, relativelystron-g instrument such as a knife blade may be inserted between flange portion 24 and the upper end 11 of cylindrical side wall portion iii of cup member A and an upward force applied to the flange portion 24 to remove cup member B from metallic cup member A.

It should be obvious to those skilled in the art that by using the grinding cup of this invention all the grinding, sanding and polishing steps in the cutting of cabochon type and faceted gem stones can be carried out through the use of a single grinding apparatus. This greatly reduces the lapidary shop space requirements and initial equipment costs. The removability of the grinding element, the wooden cup member B or lap C, while the grinding apparatus, the metallic cup member A, continues to rotate greatly reduces the time requirements for the cutting of gem stones.

It must be understood that this invention contemplates the use of a plurality of wooden cup members B or laps C with a single basic cup member A to allow the lapidist to cut gem stones of various sizes and shapes using the grin-ding cup of this invention and also to allow him to rapidly proceed through the various grinding, sanding and polishing steps of the cutting operation by using various combinations of these grinding elements and cup member A, as described above.

The invention has been described by reference to specific and preferred embodiments. It will be apparent, however, that many modifications can be made without departing from the spirit and scope of the invention, accordingly this invention should be construed not to be limited to the embodiment herein described but should be limited only by the scope of the appended claims.

I claim:

1. A grinding apparatus for gem stone working attachable to a rotatable shaft comprising in combination:

a first substantially cylindrical cup shaped member attachable to a rotating drive mechanism for rotating said member about its axis;

a second member coaxially detached within said first member and comprising a lower external portion of diameter slightly less than said cup of said first member, an upper graspable flange portion of diameter greater than said cup, said lower portion of length less than the depth of said cup whereby said upper flange portion will normally rest on the top of said first member, and

said second member including a grinding surface for said gem stone working.

2. A grinding apparatus for gem stone working according to claim 1 wherein said second member is a wood member with an internal cup shape-d grinding surface against which said gem stones will be worked.

3. A grinding apparatus for gem stone working according to claim 1 wherein said grinding surface is a relatively fiat top end surface for facet grinding said gem stone.

References Cited in the file of this patent UNITED STATES PATENTS 2,076,449 Doner Apr. 6, 1937 2,381,413 Wolff Aug. 7, 1945 2,745,225 Vonada May 15, 1956 

1. A GRINDING APPARATUS FOR GEM STONE WORKING ATTACHABLE TO A ROTATABLE SHAFT COMPRISING IN COMBINATION: A FIRST SUBSTANTIALLY CYLINDRICAL CUP SHAPED MEMBER ATTACHABLE TO A ROTATING DRIVE MECHANISM FOR ROTATING SAID MEMBER ABOUT ITS AXIS; A SECOND MEMBER COAXIALLY DETACHED WITHIN SAID FIRST MEMBER AND COMPRISING A LOWER EXTERNAL PORTION OF DIAMETER SLIGHTLY LESS THAN SAID CUP OF SAID FIRST MEMBER, AN UPPER GRASPABLE FLANGE PORTION OF DIAMETER GREATER THAN SAID CUP, SAID LOWER PORTION OF LENGTH LESS THAN THE DEPTH OF SAID CUP WHEREBY SAID UPPER FLANGE PORTION WILL NORMALLY REST ON THE TOP OF SAID FIRST MEMBER, AND SAID SECOND MEMBER INCLUDING A GRINDING SURFACE FOR SAID GEM STONE WORKING. 